Unanswered: Getting custom slider tip positioning to work

I am trying to align a slider.tip to the top, but not as far above the thumb as setting position: 'top'. I checked the source code and setting position: 'top' internally sets align: 'b-t?' and offsets: [0, -10], so I changed my config to align: 'b-t?' offsets: [0, -3], but this puts the tooltip hundreds of pixels to the right (constrained by the Viewport). Is this a bug or is there some other config I have to set to get this to work?

I've attached a screenshot showing the two appearances FWIW. Above the black line has the config {..., align: 'b-t?', offsets: [0, -3]}, and below is {..., position: 'top'}.